Interfaces, systems, and methods for use in reduced pressure tissue treatment

ABSTRACT

Systems and devices for treating a tissue site may include an interface adapted to provide a reduced pressure to a dressing. The interface may include a positive-pressure channel for delivering a positive pressure from a positive-pressure port to a positive pressure outlet. The positive-pressure channel may include a constricted portion configured to provide a pressure drop. The interface may additionally include a reduced-pressure channel adapted to deliver reduced pressure to the dressing that substantially corresponds to the pressure drop. The reduced-pressure channel may be fluidly coupled between the positive pressure channel and a side of the interface body adapted to face the dressing. Other systems and devices are disclosed.

RELATED APPLICATION

This application claims the benefit, under 35 USC §119(e), of the filingof U.S. Provisional Patent Application Ser. No. 61/679,282, entitled“INTERFACES, SYSTEMS, AND METHODS FOR USE IN REDUCED PRESSURE TISSUETREATMENT,” filed 3 Aug. 2012, which is incorporated herein by referencefor all purposes.

BACKGROUND

The present disclosure relates generally to medical treatment systems,and more particularly, but not by way of limitation, to interfaces,systems, and methods for use in reduced pressure tissue treatment.

Clinical studies and practice have shown that providing a reducedpressure in proximity to a tissue site augments and accelerates thegrowth of new tissue at the tissue site. The applications of thisphenomenon are numerous, but application of reduced pressure has beenparticularly successful in treating wounds. This treatment (frequentlyreferred to in the medical community as “negative pressure woundtherapy,” “reduced pressure therapy,” or “vacuum therapy”) provides anumber of benefits, which may include faster healing and increasedformulation of granulation tissue.

SUMMARY

According to an illustrative embodiment, a positive-pressure woundinterface for providing reduced pressure to a reduced-pressure dressingon a tissue site is presented. The positive-pressure wound interfaceincludes an interface body having a first side and a second,tissue-facing side. An inlet is formed in the interface body thatincludes a positive-pressure port and a reduced-pressure-sensing port.The positive-pressure port is fluidly isolated from thereduced-pressure-sensing port proximate the inlet. The positive-pressurewound interface further includes a positive-pressure channel extendingthough the interface body from the positive-pressure port to apositive-pressure outlet. The positive-pressure channel is configured todeliver a positive pressure through the interface body from thepositive-pressure port downstream to the positive pressure outlet. Thepositive-pressure channel includes at least one constricted portion. Thepositive-pressure wound interface further includes a reduced-pressurechannel. The reduced-pressure channel includes a first end and a second,tissue-facing end, such that the first end of the reduced-pressurechannel is fluidly coupled to the positive-pressure channel and thesecond, tissue-facing end is fluidly coupled to a tissue inlet that isproximate a tissue-facing side of the interface body. Thereduced-pressure channel extends from the positive-pressure channel tothe tissue-facing side of the interface body and is configured todeliver reduced pressure to the tissue site. The positive-pressurechannel is configured to produce the reduced pressure by a Venturieffect as positive pressure flows through the positive-pressure channeland past the reduced-pressure channel. The positive-pressure woundinterface also includes a reduced-pressure-sensing channel that extendsfrom the reduced-pressure-sensing port to the tissue-facing side of theinterface body.

In another illustrative embodiment, a system for treating a tissue siteon a patient with reduced pressure includes a manifold for placingproximate the tissue site. The manifold has a first side and a second,tissue-facing side and comprises an absorbent layer for absorbingliquids from the tissue site. The system further includes a flexiblefilm drape that has a first side and a second, tissue-facing side forcovering the first side of the manifold to form a sealed spacecontaining the manifold. The flexible film drape has an aperture formedproximate the first side of the manifold. The system includes apositive-pressure wound interface having a first side and a second,tissue-facing side for positioning over the flexible film drape. Thesecond, tissue-facing side of the interface is disposed on the flexiblefilm drape proximate the aperture. The positive-pressure wound interfaceincludes an interface body having a first side and a second,tissue-facing side, and an inlet formed in the interface body. The inlethas a positive-pressure port and a reduced-pressure-sensing port, suchthat the positive-pressure port is fluidly isolated from thereduced-pressure-sensing port proximate the inlet. The interface furtherincludes a positive-pressure channel that extends though the interfacebody from the positive-pressure port to a positive-pressure outlet. Thepositive-pressure channel is configured to deliver a positive pressurethrough the interface body from the positive-pressure port downstream tothe positive-pressure outlet. The positive-pressure channel includes atleast one constricted portion. The positive-pressure wound interfacefurther includes a reduced-pressure channel having a first end and asecond, tissue-facing end, such that the first end of thereduced-pressure channel is fluidly coupled to the positive-pressurechannel and the second, tissue-facing end is fluidly coupled to a tissueinlet that is proximate a tissue-facing side of the interface body. Thereduced-pressure channel extends from the positive-pressure channel tothe tissue-facing side of the interface body and is configured todeliver the reduced pressure to the tissue site through the aperture inthe flexible film drape. The interface is configured such that thepositive-pressure channel is configured to produce the reduced pressureby a Venturi effect as positive pressure flows through thepositive-pressure channel and past the reduced-pressure channel. Theinterface also includes a reduced-pressure-sensing channel that extendsfrom the reduced-pressure-sensing port to the tissue-facing side of theinterface body. The system further includes a pressure-sensing unitfluidly coupled to the reduced-pressure-sensing channel for measuring apressure in the reduced-pressure-sensing channel.

In yet another illustrative embodiment, a system for treating a tissuesite on a patient with reduced pressure includes a manifold for placingproximate the tissue site. The manifold has a first side and a second,tissue-facing side. The system further includes a flexible film drapefor covering the first side of the manifold to form a sealed spacecontaining the manifold. The flexible film drape has an aperture. Thesystem also includes an interface having a first side and a second,tissue-facing side for positioning over the flexible film drape. Thesecond, tissue-facing side of the interface is disposed on the flexiblefilm drape proximate the manifold. The interface includes an inlet portformed in an interface body for allowing intake of an ambient gas. Theinlet port has a first diameter at an upstream end and a second, smallerdiameter at an opposing downstream end. The interface body furtherincludes a first and second reduced-pressure channel. The firstreduced-pressure channel extends through the interface body from theinlet port to an outlet port. The second reduced-pressure channel isfluidly coupled to the first reduced-pressure channel and extends fromthe first reduced-pressure channel to the second, tissue-facing side ofthe interface. The second reduced-pressure channel is configured todeliver the reduced pressure to the tissue site when a fluid is pulledthough the inlet port with sufficient flow rate to produce the reducedpressure by way of a Venturi effect. The system further includes areduced-pressure source fluidly coupled to the outlet port for pullingthe fluid through the first reduced-pressure channel. A pressure-sensingunit is fluidly coupled to a pressure-sensing port for monitoringpressure proximate the tissue site

In yet another illustrative embodiment, provided is an interface forproviding a reduced pressure to a dressing. The interface includes aninterface body, an inlet, a positive-pressure channel, areduced-pressure channel, and a reduced-pressure sensing channel. Theinterface body has a first side and a second side, and the second sideof the interface body is adapted to face the dressing. The inlet isformed proximate the first side of the interface body, and the inlet hasa positive-pressure port and a reduced-pressure-sensing port. Thepositive-pressure channel is adapted to deliver positive pressure. Thepositive-pressure channel extends through the interface body from thepositive-pressure port to a positive-pressure outlet proximate the firstside of the interface body. The positive-pressure channel includes aconstricted portion configured to provide a pressure drop. Thereduced-pressure channel is adapted to deliver the reduced pressure tothe dressing. The reduced-pressure channel is fluidly coupled betweenthe positive-pressure channel and the second side of the interface body,and the reduced pressure delivered by the reduced-pressure channelsubstantially corresponds to the pressure drop. Thereduced-pressure-sensing channel is in fluid communication between thereduced-pressure-sensing port and the second side of the interface body.

In yet another illustrative embodiment, provided is a system fortreating a tissue site with reduced pressure. The system includes amanifold, a flexible film drape, an interface, a positive-pressuresource, and a pressure sensing unit. The manifold is for placingproximate the tissue site, and the manifold comprises an absorbent layerfor absorbing liquids from the tissue site. The flexible film drape isfor covering the manifold to form a sealed space containing themanifold, and the flexible film drape has an aperture adapted to providefluid communication with the sealed space. The interface is adapted tobe positioned over the flexible film drape, and the interface includesan interface body, an inlet, a positive-pressure channel, areduced-pressure channel, and a reduced-pressure sensing channel. Theinterface body has a first side and a second side, and the second sideis adapted to face the flexible film drape and to be in fluidcommunication with the manifold through the aperture. The inlet isformed proximate the first side of the interface body, and the inlet hasa positive-pressure port and a reduced-pressure-sensing port. Thepositive-pressure port is fluidly isolated from thereduced-pressure-sensing port proximate the inlet. The positive-pressurechannel is adapted to deliver positive pressure. The positive pressurechannel extends through the interface body from the positive-pressureport to a positive-pressure outlet proximate the first side of theinterface body. Further, the positive pressure channel includes aconstricted portion configured to provide a pressure drop. Thereduced-pressure channel is adapted to deliver a reduced pressure to themanifold. The reduced-pressure channel is fluidly coupled between thepositive-pressure channel and the second side of the interface body.Further, the reduced pressure delivered by the reduced-pressure channelsubstantially corresponds to the pressure drop. Thereduced-pressure-sensing channel is in fluid communication between thereduced-pressure-sensing port and the second side of the interface body.The positive-pressure source is fluidly coupled to the positive-pressurechannel, and the pressure-sensing unit is fluidly coupled to thereduced-pressure-sensing channel for measuring a pressure in thereduced-pressure-sensing channel.

In yet another illustrative embodiment, provided is a system fortreating a tissue site with a reduced pressure. The system includes amanifold, a flexible film drape, an interface, a reduced-pressuresource, and a pressure-sensing unit. The manifold is for placingproximate the tissue site, and the manifold has a first side and asecond side. The second side of the manifold is adapted to face thetissue site The flexible film drape is for covering the first side ofthe manifold to form a sealed space containing the manifold, and theflexible film drape has an aperture adapted to provide fluidcommunication with the sealed space. The interface is for positioningover the flexible film drape proximate the aperture, and the interfacehas a first side and a second side. The second side of the interface isadapted to face the tissue site. The interface includes an inlet port, afirst reduced-pressure channel, a second reduced-pressure channel, and apressure-sensing port. The inlet port is positioned proximate the firstside of the interface, and is adapted to intake ambient gas. Further,the inlet port includes a constricted portion having a first diameter atan upstream end and a second diameter at an opposing downstream end. Thesecond diameter is smaller than the first diameter such that theconstricted portion is adapted to provide a pressure drop. The firstreduced-pressure channel extends through the interface from the inletport to an outlet port positioned proximate the first side of theinterface. The second reduced-pressure channel is adapted to deliver thereduced pressure to the tissue site and is fluidly coupled between thefirst reduced-pressure channel and the second side of the interface. Thereduced pressure delivered by the second reduced-pressure channelsubstantially corresponds to the pressure drop. The pressure-sensingport is positioned in the second side of the interface, thereduced-pressure source is fluidly coupled to the outlet port, and thepressure-sensing unit is fluidly coupled to the pressure-sensing portfor monitoring pressure proximate the tissue site.

Other aspects, features, and advantages of the illustrative embodimentswill become apparent with reference to the drawings and detaileddescription that follow.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram, with a portion shown in cross-section, ofan illustrative embodiment of a system for treating a wound on a patientthat includes a positive-pressure wound interface configured to producereduced pressure at the wound by a Venturi effect;

FIG. 2 is a schematic, cross-sectional view of an illustrativeembodiment of the positive-pressure wound interface shown in FIG. 1;

FIG. 3 is a schematic, perspective view of an illustrative embodiment ofa portion of a system for treating a wound on a patient that includes apositive-pressure wound interface and a Coanda device;

FIG. 4 is a schematic, perspective view of an illustrative embodiment ofa Coanda device;

FIG. 5 is a schematic, perspective view, of a portion of the Coandadevice of FIG. 4 shown over a wound; and

FIG. 6 is a schematic, cross-sectional view of an illustrativeembodiment of a wound interface for use in a system for treating a woundon a patient that utilizes a Venturi effect to deliver a reducedpressure to the wound.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

In the following detailed description of the illustrative, non-limitingembodiments, reference is made to the accompanying drawings that form apart hereof. These embodiments are described in sufficient detail toenable those skilled in the art to practice the subject matter of thisdisclosure. Other embodiments may be utilized, and logical, structural,mechanical, electrical, and chemical changes may be made withoutdeparting from the scope of this disclosure. To avoid detail notnecessary to enable those skilled in the art to practice the embodimentsdescribed herein, the description may omit certain information known tothose skilled in the art. The following detailed description is providedwithout limitation and with the scope of the illustrative embodimentsbeing defined by the appended claims.

Referring to the figures and initially to FIGS. 1-2, provided is asystem 100 for treating a tissue site. The tissue site may be, forexample, a wound 102 on a patient 104. The system 100 may include apositive-pressure wound interface 106 that has an interface body 108.The interface body 108 may include a positive-pressure channel 110 and areduced-pressure channel 112. The positive-pressure channel 110 may beconfigured to create a Venturi effect as positive pressure flows throughthe positive-pressure channel 110 and past the reduced-pressure channel112. In this manner, the interface body 108 may enable the delivery ofreduced pressure to the wound 102 as the positive pressure flows throughthe positive-pressure channel 110 and past the reduced-pressure channel112.

The system 100 may further include a wound dressing 114 positionedadjacent the wound 102. The system 100 may work with many types ofdressings, but is shown in FIG. 1, for example, with the wound dressing114. The wound dressing 114 includes a wound filler 113 that may becomprised of a wound-interface layer 116 and an absorbent layer 118. Thewound filler 113 has a first side 115 and a second, tissue-facing side117. The wound-interface layer 116 may be a manifold, wicking layer, orother material for interfacing with the wound 102. A manifold refersgenerally to a substance or structure that is provided to assist inapplying reduced pressure to, delivering fluids to, or removing fluidsfrom a tissue site, such as the wound 102. The manifold includes aplurality of flow channels or pathways that distribute fluids providedto and removed from the wound 102 around the manifold. In oneillustrative embodiment, the flow channels or pathways areinterconnected to improve distribution of fluids provided to or removedfrom the wound 102. The manifold may be a biocompatible material that iscapable of being placed in contact with the wound 102 and distributingreduced pressure to the wound 102. Examples of manifolds include,without limitation, one or more of the following: devices that havestructural elements arranged to form flow channels, such as, forexample, cellular foam, open-cell foam, porous tissue collections,liquids, gels, and foams that include, or cure to include, flowchannels; porous material, such as foam, gauze, felted mat, or similarmaterial suited to a particular biological application; porous foam thatincludes a plurality of interconnected cells or pores that act as flowchannels, such as, for example, a polyurethane, open-cell, reticulatedfoam such as GranuFoam® material manufactured by Kinetic Concepts,Incorporated of San Antonio, Tex.; a bioresorbable material; or ascaffold material.

The absorbent layer 118 may absorb liquid from the wound 102. Theabsorbent layer 118 may be any material that retains liquids and maycomprise one or more of the following: Luquafleece® material, BASF 402c,Technical Absorbents 2317 available from Technical Absorbents(www.techabsorbents.com), sodium polyacrylate super absorbers,cellulosics (carboxy methyl cellulose and salts such as sodium CMC), oralginates. The absorbent layer 118 may allow fluids and exudate removedfrom the wound 102 to be stored within the wound filler 113 instead ofstoring the wound fluids remotely in a canister. As will be described inmore detail below, the wound dressing 114 may be configured to encouragethe evaporation of moisture stored within the wound filler 113 to keepthe wound filler 113 from becoming overly saturated with wound fluid. Ifthe wound filler 113 becomes overly saturated with fluid, the woundfiller 113 may not be able to absorb additional fluids from the wound102.

Continuing with FIGS. 1-2, the wound dressing 114 may further include asealing member 120 disposed over the wound filler 113 and a portion ofintact skin 122 to form a sealed space 124. The sealing member 120 mayinclude a first side 130 and a second, tissue facing side 132. Atreatment aperture 126 may be formed in the sealing member 120 toprovide fluid access to the sealed space 124. The positive-pressurewound interface 106 may be in fluid communication with the treatmentaperture 126.

The sealing member 120 may be any liquid-impervious material capable offorming the sealed space 124 into which reduced pressure may be applied.For example, the sealing member 120 may be formed from ahigh-moisture-vapor-transfer-rate material (high MVTR material) or adrape material that may be a flexible film. “Moisture Vapor TransmissionRate” or “MVTR” represents the amount of moisture that can pass througha material in a given period of time. Ahigh-moisture-vapor-transfer-rate material typically has a moisturevapor transmission rate greater than 300 g/m² per 24 hours, and moretypically 1000 g/m² per 24 hours or more The sealing member 120 allowsvapor to egress from the sealed space 124 through the sealing member 120to the atmosphere exterior to the wound dressing 114.

The sealing member 120 may comprise one or more of the following:hydrophilic polyurethane; cellulosics; hydrophilic polyamides; anINSPIRE 2301 material from Expopack Advanced Coatings of Wrexham, UnitedKingdom; a thin, uncoated polymer drape; natural rubbers; polyisoprene;styrene butadiene rubber; chloroprene rubber; polybutadiene; nitrilerubber; butyl rubber; ethylene propylene rubber; ethylene propylenediene monomer; chlorosulfonated polyethylene; polysulfide rubber;polyurethane (PU); EVA film; co-polyester; silicones; silicone drape; a3M Tegaderm® drape; a polyurethane (PU) drape, such as one availablefrom Avery Dennison Corporation of Pasadena, Calif.; polyether blockpolyamide copolymer (PEBAX), for example, from Arkema, France; or othersimilar material.

An attachment device 128, for example, an adhesive, may be coupled toall or a portion of a second, patient-facing side 132 of the sealingmember 120. The attachment device 128 may attach the sealing member 120to the portion of intact skin 122 of the patient 104 and/or a portion ofthe wound filler 113.

The performance of the sealing member 120 with respect to MVTR may beenhanced by only covering a limited surface area of the second,patient-facing side 132 of the sealing member 120 with the attachmentdevice 128. For example, only the peripheral edge or portion of thesealing member 120 may be covered, or a limited pattern may be used.According to one illustrative embodiment of a limited pattern, only 30to 60 percent of the surface area of the second, patient-facing side 132may be covered with the attachment device 128. For example, theattachment device 128 may be applied on the second, patient-facing side132 in a limited pattern, such as, for example, a grid, spaced dots,swirls, or other patterns. The positive pressure wound interface 106 maybe coupled to the first side 130 of the sealing member 120 by any of thepreviously mentioned coupling techniques, or other similar techniques.

Continuing with FIGS. 1-2, the system 100 may further include apositive-pressure source 134 fluidly coupled to the positive-pressurewound interface 106 such that the positive-pressure wound interface 106may receive positive pressure from the positive-pressure source 134. Apositive-pressure conduit 136 may couple the positive-pressure source134 to the positive-pressure wound interface 106. The positive-pressureconduit 136 may be coupled by bonding, tube locks, interference fit, orother technique to the positive-pressure wound interface 106. AlthoughFIG. 1 illustrates the positive-pressure conduit 136 coupling thepositive-pressure wound interface 106 to the positive-pressure source134, the positive-pressure source 134 may be an integral part of thewound dressing 114. Thus, in some embodiments, the positive-pressureconduit 136 may be optional. The positive-pressure source 134 may be anydevice for supplying positive pressure, such as, for example, apositive-pressure pump. In specific, non-limiting examples, thepositive-pressure source 134 may be a diaphragm pump or a disc-pump. Inone embodiment (not shown), a disc-pump may be positioned adjacent orwithin the wound dressing 114. In another embodiment (not shown), thedisc-pump may be an integral part of the wound dressing 114.

In one embodiment, the positive-pressure source 134 may be capable ofdelivering a flow rate between about 0.1 L/Min. to about 4 L/min. In aspecific, non-limiting embodiment, the positive-pressure source 134 maybe capable of providing a flow rate of about 3 L/min when thepositive-pressure source 134 is not connected to the positive-pressurewound interface 106, and a flow rate of about 1 L/Min. to about 1.5L/min at 50 mm Hg when the positive-pressure source 134 is connected tothe positive-pressure wound interface 106. In the above embodiments, theflow rate provides a fluid speed necessary to obtain the desired reducedpressure using the Venturi effect.

The amount and nature of the positive pressure supplied to thepositive-pressure wound interface 106 may vary depending on theconstruction of the positive-pressure wound interface 106 and thedesired amount or nature of the reduced pressure being supplied to thewound 102. The desired reduced pressure supplied to the wound 102 may bebetween about −5 mm Hg (−667 Pa) to about −500 mm Hg (−66.7 kPa), andmore specifically between about −75 mm Hg (−9.9 kPa) to about −300 mm Hg(−39.9 kPa). The positive pressure may be supplied continuously orintermittently, causing the reduced pressure to be applied to the wound102 either continuously or intermittently.

The positive-pressure source 134 may be housed within or used inconjunction with a pressure sensing unit 138. The positive-pressuresource 134 and the pressure sensing unit 138 may comprise a therapyunit. The pressure sensing unit 138 may contain sensors, processingunits, alarm indicators, memory, databases, software, display units, anduser interfaces that further facilitate the application of reducedpressure treatment to the wound 102. In one example, pressure-detectionsensors (not shown) located in the pressure sensing unit 138 may receivepressure data from the positive-pressure wound interface 106 via one ormore sensing lumens 140. The sensing lumens 140 may be dedicated todelivering reduced pressure data to the pressure-detection sensors. Thepressure-detection sensors may communicate with a processing unit, orcontroller 142. The controller 142 may monitor and control the reducedpressure delivered to the wound 102 by controlling, for example, theflow rate from the positive pressure source 134.

Referring now primarily to FIG. 2, but with reference to FIG. 1, thepositive-pressure wound interface 106 has a first side 144 and a second,tissue-facing side 146. The second, tissue-facing side 146 of thepositive-pressure wound interface 106 may be disposed on the sealingmember 120 proximate the treatment aperture 126. As described above, thepositive-pressure wound interface 106 may be comprised of the interfacebody 108. The interface body 108 has a first side 148 and a second,tissue-facing side 150. The positive pressure wound interface 106 may bea single, molded piece made from flexible, stable polymers such assilicones, polyurethane (PU), rubber, or similar materials. In anotherembodiment, the positive-pressure wound interface 106 may be assembledfrom two parts, each part being a different material. An inner part maybe comprised of a rigid polymer such as an acrylonitrile butadienestyrene (ABS) or a polycarbonate acrylonitrile butadienestyrene(PC/ABS). An outer part may be positioned around a portion of theinner part. The outer part may be comprised of one of the flexiblepolymers described above, such as silicones, PU, or rubber. Thepositive-pressure wound interface 106 may be assembled from two parts asdescribed above to help the positive-pressure wound interface 106 fromdeforming under thermal and pressure changes. Portions of thepositive-pressure wound interface 106 subject to air flow may havesurfaces that are smooth and substantially free of molding inclusions toavoid air turbulences.

An inlet 152 may be formed within the interface body 108. The inlet 152may include a positive-pressure port 154 and a reduced-pressure-sensingport 156 that are fluidly isolated from each other at least proximatethe inlet 152. The positive-pressure port 154 may be in fluidcommunication with, or fluidly coupled to, the positive-pressure conduit136. The reduced-pressure-sensing port 156 may be in fluidcommunication, with or fluidly coupled to, the one or more sensinglumens 140 by way of a reduced-pressure-sensing channel 157.

The positive-pressure channel 110 extends through the interface body 108from the positive-pressure port 154 to a positive-pressure outlet 160.The positive-pressure channel 110 may have a longitudinal axissubstantially parallel to the surface of the wound 102, or at an angleto the surface of the wound 102, when positioned for use. Thepositive-pressure channel 110 may be configured to deliver the positivepressure through the interface body 108 from the positive-pressure port154 downstream to the positive-pressure outlet 160. Thepositive-pressure channel 110 may have a surface that is smooth andsubstantially free of molding inclusions to avoid air turbulences withinthe positive-pressure channel 110.

In another embodiment, the positive-pressure channel 110 may be in fluidcommunication with a plurality of positive-pressure outlets 160 fordirecting flow circumferentially about the interface body 108 and overthe sealing member 120, as described further below. In yet anotherembodiment, the positive-pressure outlet 160 may be a single outlet,such as a circumferential outlet, circumscribing the interface body 108for providing circumferential flow.

To utilize the Venturi effect as desired, the positive-pressure channel110 may include at least one constricted portion 162. In a specific,non-limiting embodiment, the at least one constricted portion 162 mayhave a slope of approximately 20, 25, 30, or 40 degrees (and any numberof degrees thereinbetween) relative to the longitudinal axis of thepositive-pressure channel 110 or the longitudinal axis of theconstricted portion 162. The slope of the at least one constrictedportion 162 may be gradual to avoid air turbulence within thepositive-pressure channel 110 for a given set of operational parameterssuch as, for example, air flow velocity and pressures. Thepositive-pressure channel 110 may be configured to create a Venturieffect when experiencing sufficient fluid flow therethrough. The Venturieffect is a jet effect that results in a reduction in pressure when thevelocity of an air flow increases due to the principles of continuity.When a high flow fluid, for example air, is subjected to a constriction,the velocity of the air increases. In order to maintain the principlesof conservation of energy and mass, however, the air pressure mustdecrease in response to the increase in velocity. Therefore, thepositive-pressure wound interface 106 as a whole, including thepositive-pressure channel 110, is configured to take advantage of theVenturi effect to create a reduced pressure that may be applied to thewound 102 via the reduced-pressure channel 112.

The at least one constricted portion 162 of the positive-pressurechannel 110 may be cone shaped with a first end 174 having a firstdiameter, D1, and a second, opposing end 176 having a second diameter,D2, such that the first diameter, D1, is larger than the seconddiameter, D2. In a specific, non-limiting example, the first diameter,D1, may be between about 5 millimeters to about 10 millimeters (mm), andthe second diameter, D2, may be between about 0.2 mm to about 0.7 mm.The at least one constricted portion 162 may be formed in any suitableshape capable of inducing the Venturi effect and minimizing airturbulence within the positive-pressure wound interface 106, asdescribed above.

Bernoulli's equation may be used to optimize the construction of thepositive-pressure wound interface 106. For example, Bernoulli's equationmay be used to calculate the pressure drop for a given construction ofthe positive-pressure wound interface 106. The pressure drop maycorrespond to the amount of reduced pressure applied to the wound 102.Bernoulli's equation may be represented as follows:p₁−p₂=ρ/2(v₂̂2−v₁̂2), where ρ is the density of the air, v1 may be thevelocity of the air as it enters the at least one constricted portion162, and v2 may be the velocity of the air as it exits the at least oneconstricted portion 162. Therefore, the configuration of thepositive-pressure wound interface 106 may be modified so that a desiredpressure drop, p1-p2, is reached.

The reduced-pressure channel 112 may be fluidly coupled to thepositive-pressure channel 110 such that the reduced-pressure channel 112is in fluid communication with the positive-pressure channel 110. Thereduced-pressure channel 112 may include a first end 158 fluidly coupledto the positive-pressure channel 110 and a second, tissue-facing end 164fluidly coupled to a tissue inlet 166. The tissue inlet 166 may beproximate the second, tissue-facing side 150 of the interface body 108.The reduced-pressure channel 112 may extend from the positive-pressurechannel 110 to the tissue-facing side 150 of the interface body 108. Inone embodiment, the reduced-pressure channel 112 may be coupled to thepositive-pressure channel 110 downstream of the at least one constrictedportion 162. In another embodiment, the reduced-pressure channel 112 maybe coupled to the positive-pressure channel 110 at the at least oneconstricted portion 162. In a specific, non-limiting embodiment, thelongitudinal dimension of the reduced-pressure channel 112, whichextends from the positive-pressure channel 110 to the tissue-facing side150 of the interface body 108, may be greater than about 15 millimeters(mm). In other non-limiting embodiments, the longitudinal dimension maybe between about 5 mm to about 20 mm. The reduced-pressure channel 112may be substantially perpendicular to the longitudinal axis of thepositive-pressure channel 110. The reduced-pressure channel 112 may beconfigured to deliver reduced pressure to the wound 102 when positivepressure is pushed into the positive-pressure channel 110 and past thereduced-pressure channel 112 at an adequate speed. The reduced-pressurechannel 112 may have a surface that is smooth and substantially free ofmolding inclusions to avoid air turbulences within the positive-pressurewound interface 106.

The positive-pressure wound interface 106 may be configured so that airflowing through the positive-pressure channel 110 entrains air,including air from the reduced-pressure channel 112, that is then ventedthrough the positive-pressure outlet 160. The positive-pressure outlet160 may be configured to direct air flow circumferentially over thefirst side 130 of the sealing member 120 to enhance themoisture-vapor-transmission rate of the sealing member 120. Aspreviously mentioned, enhancing the moisture-vapor-transmission rate mayincrease the life of the wound filler 113 by keeping the wound filler113 from becoming saturated with wound fluid. In one embodiment, thepositive-pressure outlet 160 may be configured to vent directly to theatmosphere. In another embodiment, one or more ducts 168 (see FIGS.3-5), which may include conduits, baffling, or other elements, may becoupled to the positive-pressure outlet 160 for further directingpositive flow over the first side 130 of the sealing member 120. The oneor more ducts 168 may include or be attached to a Coanda device as willbe described in more detail below with reference to FIGS. 3-5.

The wound dressing 114 may further comprise a hydrophobic filter 170positioned adjacent the tissue inlet 166 for preventing wound exudatefrom entering the reduced-pressure channel 112. In another embodiment,the hydrophobic filter 170 may be fluidly coupled anywhere in thereduced-pressure channel 112.

In one embodiment, a regulating valve 172 may be associated with thereduced pressure channel 112 for regulating the amount of reducedpressure being supplied to the wound 102 independently of the air speedin the positive-pressure chamber 110. The regulating valve 172 mayprovide pressure regulation at the wound 102 that is independent of thepressure in the positive-pressure channel 110.

In another embodiment, the controller 142 may be used to vary the amountof positive pressure provided by, for example, the positive pressuresource 134, to control the amount of reduced pressure applied at thewound 102. The controller 142 may receive feedback from the pressuresensing unit 138 that indicates the amount of pressure being applied tothe wound 102. Based on the feedback, the controller 142 may signal thepositive-pressure source 134 to vary or modulate the amount of positivepressure generated by the positive-pressure source 134 so that thereduced pressure applied to the wound 102 reaches a desired level. Powerprovided to the positive-pressure source 134 may be varied or modulatedto vary the amount of positive pressure generated by the positivepressure source 134. A control valve (not shown) may also be utilized tovary the amount of positive pressure. The controller 142 may allow thesystem 100 to operate over a range of desired reduced pressure levels.The controller 142 may be configured to operate at a number of presetreduced pressure levels that may be selected by or provided to ahealthcare provider. The controller 142 may improve the efficiency ofthe positive-pressure source 134 by modulating power to the positivepressure source 134 based on the desired amount of positive pressure tobe generated. In the instance that a battery is used to power thepositive-pressure source 134, the battery life may be extended in thismanner.

The controller 142 may be coupled to an atmospheric pressure sensor (notshown). The atmospheric pressure may vary depending on various elements,including the altitude in which the system 100 is operating. The effectsof variable atmospheric pressure may affect the performance of thesystem 100. The atmospheric pressure sensor may allow the controller 142to account for variances in the atmospheric pressure and signal orcommand the positive-pressure source 134 accordingly. In other words,the controller 142 may signal the positive-pressure source 134 toincrease or decrease the pressure output based on variances inatmospheric pressure.

Referring now primarily to FIGS. 3-5, the system 100 illustrated in FIG.1 may further include a Coanda device 210 associated with thepositive-pressure wound interface 106. The Coanda device 210 may receivefluid exiting the positive-pressure wound interface 106 to encourageairflow over the wound dressing 114 for enhancing evaporation of liquidsfrom the wound dressing 114. Among other benefits, enhanced evaporationof liquids from the wound dressing 114 may allow the wound dressing 114to process relatively more fluids. The positive-pressure wound interface106 and the Coanda device 210 may be associated with one another inseveral ways. For example, the positive-pressure wound interface 106 maybe coupled to the Coanda device 210, formed integrally with the Coandadevice 210, or placed adjacent to the Coanda device 210. The Coandadevice 210 may be coupled to the positive pressure outlet 160 of thepositive-pressure wound interface 106 by the one or more ducts 168.

In other embodiments, other entrainment devices may be used as theCoanda device 210 to entrain air and direct the air over the wounddressing 114 to achieve the desired air-flow. These other entrainmentdevices, such as, for example, a Conventional Ejector, may be used toentrain air to create a more voluminous flow based on the presence of ahigh pressure flow. The Conventional Ejector may utilize a primary flowlocated proximate to an available secondary air source that is “dragged”by an airfoil shape to have the effect of an air-multiplier.

The Coanda device 210 may be a device for entraining air, as describedabove, that utilizes the Coanda effect. The Coanda effect is generally aphenomena in which a flow attaches itself to a nearby surface andremains attached even as the surface (Coanda surface) pulls away fromthe initial direction of the flow. As the flow curves away, the flow mayentrain surrounding fluids and increase the volume of the flow. TheCoanda surface close to the flow may restrict the entrainment in thatregion, and as the flow accelerates to try to balance a momentumtransfer, a pressure differential may develop across the flow thatchanges or deflects the direction of the flow closer to the surface. TheCoanda effect is named for Henri Coanda and the concept is described inU.S. Pat. No. 2,052,869, granted to Coanda.

Thus, as shown in FIG. 5, the Coanda device 210 creates a desiredairflow as suggested by arrows 240. The Coanda device 210 may be fluidlycoupled by the one or more ducts 168 to the positive-pressure outlet 160formed in the positive-pressure wound interface 106. Thepositive-pressure outlet 160 may supply a relatively high pressure airto the Coanda device 210. In one embodiment, the discharge flow rateexiting the positive-pressure outlet 160 may be approximately 2 L/min orgreater. As used herein, air is intended to cover other working gasesthat may be used to help remove moisture. The Coanda device 210 mayreceive positive pressure air from the one or more ducts 168 and developan enhanced air flow that is delivered from the Coanda device 210 overthe first side 130 of the sealing member 120. As the air moves acrossthe wound dressing 114, any moisture or vapor on the first side 130 ofthe sealing member 120 may be removed. This may increase or maintain astrong relative humidity gradient across the sealing member 120 thathelps remove liquid from the wound dressing 114, which may enhance theability of the wound dressing 114 to process liquids.

Continuing with FIGS. 3-5, the Coanda device 210 may include an annularnozzle 246. The annular nozzle 246 may form a central opening 248. Thecentral opening 248 may surround much of the interface body 108 and aportion of the interface body 108 may extend through the central opening248. The annular nozzle 246 may have walls 250 that form an interiorpassage 252. A nozzle opening 254 may be formed on the annular nozzle246 on a portion in or near the central opening 248. A portion of thewalls 250 may form a Coanda surface 256 proximate to and downstream fromthe nozzle opening 254. The fluid or air exiting the nozzle opening 254may entrain additional fluid from the central opening 248 as the airflow follows the Coanda surface 256. The flow of air from the nozzleopening 254 plus the entrained air from the central opening 248 mayproduce a combined fluid flow.

For the configuration shown in FIG. 5, air may be moved out of thenozzle opening 254 as suggested by arrows 258. The airflow may entrainadditional air from the central opening 248 as suggested by arrows 260.The combined fluid flow is suggested by the arrows 240. Based on theCoanda effect, if a volume V₁ of air is delivered by the one or moreducts 168 to the Coanda device 210 over a time T, and a volume V₂ of airis delivered through the central opening 248 of the Coanda device 210over the time T, the combined air flow (V₂+V₁) will be enhanced or morevolumuous than the original supply (V₁). The Coanda device 210 mayoperate as described in various positions, and thus, the positioningdepicted in FIGS. 3-5 may be may be flipped or rotated for orienting thenozzle opening 254 to discharge air away from a base portion of theinterface body 108 such that air recruited from the central opening 248is pulled from proximate the first side 130 of the sealing member 120.

A number of devices or elements may be used to position the Coandadevice 210 to have a flow clearance 268 between the Coanda device 210and the sealing member 120. For example, referring to FIG. 3, aplurality of rib members 270 may be used to suspend the annular nozzle246 of the Coanda device 210 to create the flow clearance 268.

Referring now primarily to FIG. 6, presented is a reduced-pressure woundinterface 306 for use with a reduced-pressure source (not shown). Thereduced-pressure source may be analogous to the positive-pressure source134, but adapted to provide reduced-pressure. The reduced-pressure woundinterface 306 and the reduced-pressure source may be part of areduced-pressure treatment system used to treat a wound with reducedpressure. The reduced-pressure wound interface 306 may be analogous inmany respects to the positive-pressure wound interface 106 illustratedin FIG. 1. Namely, the reduced-pressure wound interface 306 may beconfigured to create a Venturi effect that develops the reduced pressureat a wound. The reduced-pressure wound interface 306 may have aninterface body 308 that may include a first reduced-pressure channel 310and a second reduced-pressure channel 312. The first reduced-pressurechannel 310 may be configured to create a Venturi effect as air ispulled through the first reduced-pressure channel 310 and past thesecond reduced-pressure channel 312. Air may be pulled through the firstreduced-pressure channel 310 by the reduced-pressure source. Theinterface body 308 may enable the delivery of reduced pressure to thewound as the air flows through the first reduced-pressure channel 310and past the second reduced-pressure channel 312.

A wound dressing 314, analogous to the wound dressing 114 of FIG. 1, maybe positioned adjacent the wound. Similar to the wound dressing 114, thewound dressing 314 may include a wound filler 313 that may be comprisedof a wound-interface layer and an absorbent layer (not shown). Thewound-interface layer may be a manifold as described above. In oneembodiment, the wound filler 313 may be a manifold only since liquidsmay be removed directly as described herein. The wound filler 313 may becovered by a sealing member 320. The sealing member 320 may be formedfrom a high-moisture-vapor-transfer-rate material (high MVTR material)or a drape material that may be a flexible film.

The amount, nature, or pressure of the air pulled through the firstreduced-pressure channel 310 may vary depending on the construction ofthe reduced-pressure wound interface 306, ambient conditions, and thedesired amount of the reduced pressure being supplied to the wound. Thedesired reduced pressure supplied to the wound may be between about −5mm Hg (−667 Pa) to about −500 mm Hg (−66.7 kPa), and more specificallybetween about −75 mm Hg (−9.9 kPa) to about −300 mm Hg (−39.9 kPa). Thereduced-pressure source may cause air to be pulled through the firstreduced-pressure channel 310 either continuously or intermittently,causing the reduced pressure to be applied to the wound eithercontinuously or intermittently.

The reduced-pressure source may be housed with or used in conjunctionwith a pressure-sensing unit (not explicitly shown but analogous to thepressure sensing unit 138 in FIG. 1). The pressure-sensing unit may befluidly coupled to a pressure-sensing port 356 formed in the interfacebody 308 such that the pressure-sensing port 356 has an opening adjacenta tissue-facing side of the interface body 308. The pressure-sensingunit may receive a pressure sample from the pressure-sensing port 356for monitoring pressure at the wound. A controller may be connected tothe sensing unit and the reduced-pressure source. The controller maysend signals or commands to the reduced-pressure source based on datareceived from the sensing unit to regulate the amount of reducedpressure supplied to the wound.

An inlet port 352 may be formed within the interface body 308. The inletport 352 may allow the intake of an ambient gas. The inlet port 352 maybe shaped such that the inlet port 352 has a first diameter, D1, at anupstream end, and a second diameter, D2, at an opposing, downstream end.The first diameter, D1, may be larger than the second diameter, D2. Inother words, the inlet port 352 may have a constricted portion definedby the first and the second diameters, D1 and D2. The inlet port 352 mayhave a slope of approximately 20, 25, 30, 35, or 40 degrees (and anynumber of degrees thereinbetween) relative to a longitudinal axis of thefirst reduced-pressure channel 310 or the longitudinal axis of theconstricted portion.

The first reduced-pressure channel 310 may extend through the interfacebody 308 from the inlet port 352 to an outlet port 360. The firstreduced-pressure channel 310 may have a longitudinal axis that issubstantially parallel to the surface of the wound, or at an angle tothe surface of the wound, when positioned for use. The firstreduced-pressure channel 310 may be configured to pull air through theinterface body 308 from the inlet port 352 downstream to the outlet port360. The first reduced-pressure channel 310 may have a surface that issmooth and substantially free of molding inclusions to avoid airturbulences within the first reduced-pressure channel 310.

The second reduced-pressure channel 312 may be coupled to the firstreduced-pressure channel 310 such that the second reduced-pressurechannel 312 is in fluid communication with the first reduced-pressurechannel 310. The second reduced-pressure channel 312 may extend from thefirst reduced-pressure channel 310 to the tissue-facing side of thereduced-pressure wound interface 306. The second reduced-pressurechannel 312 may be configured to deliver reduced pressure to the woundwhen a fluid or air is pulled through the inlet port 352 with sufficientflow rate to produce the reduced pressure at the wound by way of theVenturi effect. In one embodiment, the second reduced-pressure channel312 may be coupled to the first reduced-pressure channel 310 downstreamof the constricted portion. In another embodiment, the secondreduced-pressure channel 312 may be coupled to the firstreduced-pressure channel 310 at the constricted portion. In a specific,non-limiting embodiment, the longitudinal dimension of the secondreduced-pressure channel 312, which extends from the firstreduced-pressure channel 310 to the tissue-facing side of the interfacebody 308, may be greater than 15 millimeters (mm). In other non-limitingembodiments, the longitudinal dimension may be between about 5 mm toabout 20 mm. The second reduced-pressure channel 312 may besubstantially perpendicular to, or at an angle to, the longitudinal axisof the first reduced-pressure channel 310. The second reduced-pressurechannel 312 may have a surface that is smooth and substantially free ofmolding inclusions to avoid air turbulences within the interface 306.

The reduced-pressure wound interface 306 may be configured so that airpulled into the first reduced-pressure channel 310 via the inlet port352 entrains air surrounding the sealing member 320. The air flow causedby the air being pulled into the inlet port 352 may cause air to flowover the sealing member 320 to enhance the moisture-vapor-transmissionrate of the sealing member 320. As previously mentioned, enhancing themoisture-vapor-transmission rate may increase the life of the woundfiller 313 by keeping the wound filler 313 from becoming overlysaturated with wound fluid.

The wound dressing 314 may further comprise a hydrophobic filter 370positioned between the wound and the first reduced-pressure channel 310.In one embodiment, the hydrophobic filter 370 may be positioned withinthe second reduced-pressure channel 312. In another embodiment, nohydrophobic filter may be used and wound exudate removed from the woundmay be pulled through the first and second reduced-pressure channels310, 312 and deposited in a canister (not shown).

In one embodiment, a regulating valve 372 may be associated with thesecond reduced-pressure channel 312 for regulating the amount of reducedpressure being supplied to the wound. The regulating valve 372 mayprovide pressure regulation at the wound that is independent of thereduced pressure in the first reduced-pressure channel 310.

The above description of illustrative embodiments is given by way ofexample. Although various embodiments have been described above with acertain degree of particularity, or with reference to one or moreindividual embodiments, modifications may be made by those skilled inthe art without departing from the scope of the appended claims.Further, the steps of the methods described herein may be carried out inany suitable order, or simultaneously where appropriate. Aspects of anyof the embodiments described above may be combined with aspects of anyof the other embodiments described to form further examples havingcomparable or different properties and addressing the same or differentproblems. Thus, the benefits and advantages described above may relateto one embodiment or may relate to several embodiments.

We claim:
 1. An interface for providing a reduced pressure to adressing, the interface comprising: an interface body having a firstside and a second side, the second side adapted to face the dressing; aninlet formed proximate the first side of the interface body, the inlethaving a positive-pressure port and a pressure-sensing port; apositive-pressure channel adapted to deliver positive pressure andextending through the interface body from the positive-pressure port toa positive-pressure outlet proximate the first side of the interfacebody, wherein the positive-pressure channel includes a constrictedportion configured to provide a pressure drop; a reduced-pressurechannel adapted to deliver the reduced pressure to the dressing, thereduced-pressure channel fluidly coupled between the positive-pressurechannel and the second side of the interface body, wherein the reducedpressure substantially corresponds to the pressure drop; and apressure-sensing channel in fluid communication between thepressure-sensing port and the second side of the interface body.
 2. Theinterface of claim 1, wherein the reduced-pressure channel has alongitudinal dimension extending between the positive-pressure channeland the second side of the interface body that is greater than 15millimeters.
 3. The interface of claim 1, wherein the positive-pressurechannel has a longitudinal axis substantially parallel to the secondside of the interface body, and wherein the reduced-pressure channel issubstantially perpendicular to the positive-pressure channel.
 4. Theinterface of claim 1, further comprising a hydrophobic filter positionedadjacent the second side of the interface body and adapted to bepositioned in fluid communication between the reduced-pressure channeland the dressing.
 5. The interface of claim 1, further comprising aregulating valve associated with the reduced pressure channel that isadapted to regulate an amount of the reduced pressure being delivered tothe dressing.
 6. The interface of claim 1, further comprising at leastone duct in fluid communication with the positive-pressure outlet,wherein the at least one duct is configured to direct flow over a drape.7. The interface of claim 1, wherein the constricted portion has a firstdiameter at an upstream end and a second diameter at an opposingdownstream end, the second diameter being smaller than the firstdiameter, and wherein the constricted portion has a slope of 30 degreesrelative to a longitudinal axis of the positive-pressure channel.
 8. Theinterface of claim 1, wherein the positive-pressure outlet is configuredto vent to the atmosphere.
 9. The interface of claim 1, wherein thereduced-pressure channel is fluidly coupled to the positive-pressurechannel downstream of the constricted portion and between theconstricted portion and the positive-pressure outlet.
 10. The interfaceof claim 1, wherein the reduced-pressure channel is fluidly coupled tothe positive-pressure channel at the constricted portion.
 11. Theinterface of claim 1, further comprising: a hydrophobic filter disposedproximate the second side of the interface body; a regulating valveassociated with the reduced-pressure channel that is adapted to regulatean amount of the reduced pressure being delivered to the dressing; atleast one duct associated with the positive-pressure outlet andconfigured to direct flow over a drape; wherein the reduced-pressurechannel has a longitudinal dimension extending between thepositive-pressure channel and the second side of the interface body thatis greater than 15 millimeters; wherein the positive-pressure channelhas a longitudinal axis substantially parallel to the second side of theinterface body, and wherein the reduced-pressure channel issubstantially perpendicular to the positive-pressure channel; whereinthe constricted portion has a slope greater than 20 degrees relative toa longitudinal axis of the positive-pressure channel; wherein thepositive-pressure outlet is configured to vent to atmosphere; andwherein the positive-pressure port is fluidly isolated from thepressure-sensing port proximate the inlet.
 12. A system for treating atissue site with reduced pressure, comprising: a manifold for placingproximate the tissue site, the manifold comprising an absorbent layerfor absorbing liquids from the tissue site; a flexible film drape forcovering the manifold to form a sealed space containing the manifold,the flexible film drape having an aperture adapted to provide fluidcommunication with the sealed space; an interface adapted to bepositioned over the flexible film drape; wherein the interfacecomprises: an interface body having a first side and a second side, thesecond side adapted to face the flexible film drape and to be in fluidcommunication with the manifold through the aperture, an inlet formedproximate the first side of the interface body, the inlet having apositive-pressure port and a pressure-sensing port, wherein thepositive-pressure port is fluidly isolated from the pressure-sensingport proximate the inlet, a positive-pressure channel adapted to deliverpositive pressure and extending through the interface body from thepositive-pressure port to a positive pressure outlet proximate the firstside of the interface body, wherein the positive-pressure channelincludes a constricted portion configured to provide a pressure drop, areduced-pressure channel adapted to deliver a reduced pressure to themanifold, the reduced-pressure channel fluidly coupled between thepositive-pressure channel and the second side of the interface body,wherein the reduced pressure substantially corresponds to the pressuredrop, and a pressure-sensing channel in fluid communication between thepressure-sensing port and the second side of the interface body; apositive-pressure source fluidly coupled to the positive-pressurechannel; and a pressure-sensing unit fluidly coupled to thepressure-sensing channel for measuring a pressure in thepressure-sensing channel.
 13. The system of claim 12, further comprisingat least one duct fluidly coupled to the positive-pressure outlet fordirecting positive flow over the flexible film drape.
 14. The system ofclaim 13, wherein the at least one duct comprises a Coanda deviceadapted to entrain air and to increase a volume of the positive flow.15. The system of claim 12, further comprising a controller coupled tothe positive-pressure source for regulating an amount of the positivepressure delivered to the positive-pressure port.
 16. The system ofclaim 12, wherein the reduced-pressure channel has a longitudinaldimension extending between the positive-pressure channel and the secondside of the interface body that is greater than 15 millimeters.
 17. Thesystem of claim 12, wherein the positive-pressure channel has alongitudinal axis that is substantially parallel to the second side ofthe interface body, and wherein the reduced-pressure channel issubstantially perpendicular to the positive-pressure channel.
 18. Thesystem of claim 12, further comprising a hydrophobic filter positionedadjacent the second side of the interface body and adapted to bepositioned in fluid communication between the reduced-pressure channeland the manifold.
 19. The system of claim 12, further comprising aregulating valve associated with the reduced pressure channel that isadapted to regulate an amount of the reduced pressure being delivered tothe tissue site.
 20. The system of claim 12, wherein the constrictedportion has a first diameter at an upstream end and a second diameter atan opposing downstream end, the second diameter being smaller than thefirst diameter, and wherein the at least one constricted portion has aslope of 30 degrees relative to a longitudinal axis of thepositive-pressure channel.
 21. The system of claim 12, wherein thepositive-pressure outlet is configured to vent to the atmosphere. 22.The system of claim 12, wherein the reduced-pressure channel is fluidlycoupled to the positive-pressure channel downstream of the at least oneconstricted portion and between the constricted portion and thepositive-pressure outlet.
 23. The system of claim 12, wherein thereduced-pressure channel is fluidly coupled to the positive-pressurechannel at the at least one constricted portion.
 24. A system fortreating a tissue site with a reduced pressure, comprising: a manifoldfor placing proximate the tissue site, the manifold having a first sideand a second side, the second side of the manifold adapted to face thetissue site; a flexible film drape for covering the first side of themanifold to form a sealed space containing the manifold, the flexiblefilm drape having an aperture adapted to provide fluid communicationwith the sealed space; an interface for positioning over the flexiblefilm drape proximate the aperture, the interface having a first side anda second side, the second side of the interface adapted to face thetissue site, the interface comprising: an inlet port positionedproximate the first side of the interface and adapted to intake ambientgas, the inlet port comprising a constricted portion having a firstdiameter at an upstream end and a second diameter at an opposingdownstream end, wherein the second diameter is smaller than the firstdiameter, and wherein the constricted portion is adapted to provide apressure drop, a first reduced-pressure channel extending through theinterface from the inlet port to an outlet port positioned proximate thefirst side of the interface, a second reduced-pressure channel adaptedto deliver the reduced pressure to the tissue site, the secondreduced-pressure channel fluidly coupled between the firstreduced-pressure channel and the second side of the interface, whereinthe reduced pressure substantially corresponds to the pressure drop, anda pressure-sensing port positioned in the second side of the interface;a reduced-pressure source fluidly coupled to the outlet port; and apressure-sensing unit fluidly coupled to the pressure-sensing port formonitoring pressure proximate the tissue site.
 25. The system of claim24, further comprising a controller adapted to be coupled to thereduced-pressure source for regulating an amount of the reduced pressuredelivered to the tissue site
 26. The system of claim 24, wherein thesecond reduced-pressure channel has a longitudinal dimension extendingbetween the first reduced-pressure channel and the second side of theinterface that is greater than 15 millimeters.
 27. The system of claim24, wherein the first reduced-pressure channel has a longitudinal axissubstantially parallel to the second side of the interface, and whereinthe second reduced-pressure channel is substantially perpendicular tothe first reduced-pressure channel.
 28. The system of claim 24, furthercomprising a hydrophobic filter adapted to be positioned between thetissue site and the first reduced-pressure channel.
 29. The system ofclaim 24, further comprising a regulating valve associated with thesecond reduced-pressure channel that is adapted to regulate an amount ofthe reduced pressure being delivered to the tissue site.
 30. The systemof claim 24, wherein the inlet port has a slope of 30 degrees relativeto the longitudinal axis of the first reduced-pressure channel.
 31. Thesystem of claim 24, further comprising a canister for collecting exudatedrawn from the tissue site.